Gallien-Krueger Backline 150 Guitar Amp HeadNotes Some pots are dirty scratchy. May require electronic cleaning, but only happens when knobs are turned. A Gallien Krueger Backline 150 Guitar Amp Head in Very Good condition! At Evolution Music, we attempt to highlight cosmetic defects (if any) by picturing every angle of every piece of gear so you know exactly what you are getting. We always picture any and all accessories too. What you see is what you will get so please check out the pictures!